365 Cubic inch engine - BHP

[bazilman]

Hi Guys and girls. I own a '57 Fleetwood with its original 6.0 litre 365 Cubic inch engine. The literature I have states that engine (from new) was rated at 300 BHP, but I am assuming that's at the flywheel, not at the rear wheels ? The reason I am asking is that tomorrow I am putting the car on a rolling road and I would like to know what BHP (at the rear wheels) the car originally came with from the factory so I can then find out how many horses I have lost over the last 62 years and then hopefully find a way to get some of them back. I hope that all makes sense ? Any help will be very much appreciated.   

[The Tassie Devil(le)]

G'day Craig,

The Factory Horsepower figures were obtained with a very bare engine, on a dyno.

No fan, Water Pump or Alternator fitted, and optimal exhaust, and possibly no air cleaner.

To say that it puts out 300 BHP, at the rear wheels, sitting within the car chassis, driving everything that takes power out of the engine, you would probably only see about 150 HP at the rear wheels, and maybe not even that.

There is power loss with fan belts, fan, generator, Transmission, right through to the rear axle gears.   The age of the motor won't diminish the power much, so long as the internals are in good condition, but worn rings, leaking valve seats etc will also cause a loss.

Would be interesting to see what it actually shows on the dial.

Bruce.

[wbdeford]

You might find this interesting.....I don't know how accurate it is:  Source:  https://www.automobile-catalog.com/curve/1957/327125/cadillac_fleetwood_sixty_special_sedan_hydra-matic.html

1000 rpm:

170.2 Nm / 125.5 lb-ft / 17.8 kW / 24.2 PS / 23.9 hp

1100 rpm:

207.5 Nm / 153 lb-ft / 23.9 kW / 32.5 PS / 32 hp

1200 rpm:

242.6 Nm / 178.9 lb-ft / 30.5 kW / 41.5 PS / 40.9 hp

1300 rpm:

275.6 Nm / 203.2 lb-ft / 37.5 kW / 51 PS / 50.3 hp

1400 rpm:

306.4 Nm / 226 lb-ft / 44.9 kW / 61.1 PS / 60.2 hp

1500 rpm:

335.2 Nm / 247.2 lb-ft / 52.7 kW / 71.6 PS / 70.6 hp

1600 rpm:

361.8 Nm / 266.8 lb-ft / 60.6 kW / 82.4 PS / 81.2 hp

1700 rpm:

386.2 Nm / 284.8 lb-ft / 68.8 kW / 93.5 PS / 92.1 hp

1800 rpm:

408.6 Nm / 301.3 lb-ft / 77 kW / 104.7 PS / 103.2 hp

1900 rpm:

428.8 Nm / 316.2 lb-ft / 85.3 kW / 116 PS / 114.3 hp



2000 rpm:

446.9 Nm / 329.6 lb-ft / 93.6 kW / 127.3 PS / 125.4 hp

2100 rpm:

462.9 Nm / 341.4 lb-ft / 101.8 kW / 138.4 PS / 136.4 hp

2200 rpm:

476.7 Nm / 351.5 lb-ft / 109.8 kW / 149.4 PS / 147.2 hp

2300 rpm:

488.4 Nm / 360.2 lb-ft / 117.6 kW / 160 PS / 157.6 hp

2400 rpm:

498 Nm / 367.3 lb-ft / 125.2 kW / 170.2 PS / 167.7 hp

2500 rpm:

505.4 Nm / 372.7 lb-ft / 132.3 kW / 180 PS / 177.3 hp

2600 rpm:

510.7 Nm / 376.6 lb-ft / 139.1 kW / 189.1 PS / 186.3 hp

2700 rpm:

513.9 Nm / 379 lb-ft / 145.3 kW / 197.6 PS / 194.7 hp

2800 rpm:

515 Nm / 379.8 lb-ft / 151 kW / 205.4 PS / 202.4 hp

2900 rpm:

514.7 Nm / 379.6 lb-ft / 156.3 kW / 212.6 PS / 209.5 hp



3000 rpm:

513.9 Nm / 379 lb-ft / 161.5 kW / 219.6 PS / 216.3 hp

3100 rpm:

512.5 Nm / 377.9 lb-ft / 166.4 kW / 226.3 PS / 222.9 hp

3200 rpm:

510.6 Nm / 376.5 lb-ft / 171.1 kW / 232.7 PS / 229.3 hp

3300 rpm:

508.1 Nm / 374.7 lb-ft / 175.6 kW / 238.8 PS / 235.3 hp

3400 rpm:

505.1 Nm / 372.5 lb-ft / 179.8 kW / 244.6 PS / 241 hp

3500 rpm:

501.5 Nm / 369.8 lb-ft / 183.8 kW / 250 PS / 246.3 hp

3600 rpm:

497.3 Nm / 366.7 lb-ft / 187.5 kW / 255 PS / 251.2 hp

3700 rpm:

492.6 Nm / 363.3 lb-ft / 190.9 kW / 259.6 PS / 255.8 hp

3800 rpm:

487.4 Nm / 359.4 lb-ft / 194 kW / 263.8 PS / 259.9 hp

3900 rpm:

481.6 Nm / 355.2 lb-ft / 196.7 kW / 267.5 PS / 263.6 hp



4000 rpm:

475.2 Nm / 350.4 lb-ft / 199.1 kW / 270.7 PS / 266.7 hp

4100 rpm:

468.3 Nm / 345.4 lb-ft / 201.1 kW / 273.5 PS / 269.4 hp

4200 rpm:

460.9 Nm / 339.9 lb-ft / 202.7 kW / 275.7 PS / 271.6 hp

4300 rpm:

452.9 Nm / 334 lb-ft / 203.9 kW / 277.4 PS / 273.3 hp

4400 rpm:

444.3 Nm / 327.7 lb-ft / 204.7 kW / 278.4 PS / 274.3 hp

4500 rpm:

435 Nm / 320.8 lb-ft / 205 kW / 278.8 PS / 274.7 hp

4600 rpm:

425.6 Nm / 313.8 lb-ft / 205 kW / 278.8 PS / 274.7 hp

4700 rpm:

414.8 Nm / 305.9 lb-ft / 204.2 kW / 277.7 PS / 273.6 hp

4800 rpm:

401.3 Nm / 295.9 lb-ft / 201.7 kW / 274.3 PS / 270.3 hp

4900 rpm:

385.1 Nm / 284 lb-ft / 197.6 kW / 268.8 PS / 264.8 hp



5000 rpm:

366.5 Nm / 270.3 lb-ft / 191.9 kW / 261 PS / 257.2 hp

[Cadillac Jack 82]

Compared with other cars of that era it definitely has a lot more pickup and go.  Its not a sports car but you can definitely feel the difference between a 55 and a 57 in terms of performance.

[Caddyholic]

I put my 61 rebuilt 390 on a chassis Dyno abut 5 years ago and the HP Peaked at 186.  I will post the print out later.

[fishnjim]

Seems low.   The '57 chart #'s looks about right.   
Rule of thumb is about 20% loss for auto trans and driveline to get @ rear wheel #s. 
There's a difference between HP and BHP.   BHP takes in the losses and what he asked for.
Engine dyno measures HP(flywheel), Chassis(rear wheel) dyno measures ~BHP (WHP).   
We engine dynoed my '58 365 after rebuild with 3x2s and it made a solid 300 HP above 4500, even though the "book" says 310-335.   But the vacuum advance was not hooked up.   

So if you're only seeing 186, ~50%, somethings wrong or memory off.
I'd think comparing 0-60 times would be a better indicator of degradation, but is the data available for your car from new?

[INTMD8]

^ Vacuum advance wouldn't add anything at wide open throttle so wouldn't change the number.

Is your 365 stock?  Ran with accessories/fan and full exhaust?

186 at the wheels doesn't sound too far off to me.

I'll have to throw my heap on the dyno and see what it does.

[Roger Zimmermann]

Seems low.   The '57 chart #'s looks about right.   
Rule of thumb is about 20% loss for auto trans and driveline to get @ rear wheel #s. 

Export models had low compression pistons. The power in the published chart is in SAE gross which is just an illusion.
The 20% loss is not valid for all vehicles. The ones with power steering, A/C and restricted exhaust + automatic transmission may have more loss than 20%. It's bout the same to try to convert c/p lamps output with watts.

[klinebau]

Keep in mind that no two dynos read the same.  It is up to the operator to calibrate them and it should be done periodically.  It is not uncommon for a dyno to read a little high as this makes the customer happier.  Rather than looking at absolute numbers, a better use of a dynamometer is to look at relative changes as tuning is being performed.

[Caddyholic]

Has anyone else on here put there stock engine car on a chassis Dyno? As far as advertised HP goes Gross ver. Net. If you look at the 71 472 gross advertised rating it is 345. If nothing in the engine changed in 72 the net advertised was 220. 125 hp or 36 percent drop. My 390 gross advertised HP is 325. So the theretical net would be .64 times that at  208. 

I did not run my engine past 5000 on the dyno and the tech wanted the car to stay in high gear. We could not figure out how to get around the transmission downshifting. I did 4 pulls
3 in D1 and 1 in D2.

[wbdeford]

I'd think comparing 0-60 times would be a better indicator of degradation, but is the data available for your car from new?

That's what I did with my 58.....got the advertised 0-60 number and called it "good".

[Eric DeVirgilis CLC# 8621]

The reason I am asking is that tomorrow I am putting the car on a rolling road and I would like to know what BHP (at the rear wheels) the car originally came with from the factory so I can then find out how many horses I have lost over the last 62 years and then hopefully find a way to get some of them back.

The best thing is to make sure the engine is tuned up to spec, the carb rebuilt as needed and the shift rod is adjusted. Unless you're looking to spend big $$$ on major modifications, that's all you can do.

None of these cars were expected, nor designed to compete on the drag strip. Better to take a page from the RR playbook regarding HP specs which for years the manufacturer steadfastly refused to publish. Instead it was simply described as "sufficient".  The same applies to a '57 Fleetwood Sixty Special.

["Cadillac Kid" Greg Surfas 15364]

Cadillac motors (at least through the 500 inch series) have always been about torque, not horsepower, Even my hot rod 73 with a 511 inch warmed over motor only makes 560 net HP at  5500 RPM, but it makes over 600 Lb/Ft of torque from 3000- 5000 rpm,. It is low speed torque , not horsepower that gets 2-1/2 tons of iron moving.
Greg Surfas

[klinebau]

Even my hot rod 73 with a 511 inch warmed over motor ONLY makes 560 net HP at  5500 RPM

[INTMD8]

It is low speed torque , not horsepower that gets 2-1/2 tons of iron moving.
Greg Surfas

Although I understand what you're trying to say I still have to take issue with that statement as torque and horsepower are interrelated.

(You didn't increase low speed torque without increasing low speed horsepower is well)

["Cadillac Kid" Greg Surfas 15364]

Jim,,
Horsepower is a calculation:  HP=Torque(T) x Rotational speed (N) / 5250. you DO increase HP when you increase torque, but the "big block (500") Cadillac motors are designed with a "flat" torque curve. meaning maximum torque is typically developed at something like 2800 RPM and stays near maximum until (stock motors) just about 4000 RPM. With something like a small block Chevrolet the torque curve shows it reaching Max at about 4500 RPM.Torque is the "grunt" that gets things going.  Diesels have tremendous torque. Typical ratings for line haul trucks might be 300 HP and 1200 Lb/Ft. of torque.
Cadillac motors (typically all from 1949-1976) were designed specifically to develop high torque ratings at low engine speed.
Greg Surfas

[INTMD8]

Yes of course.